What is the electronic structure with respect to carbon in calcium carbide, #Ca^(2+)C_2^(-)#?
The answer is 1: 6 electrons
The number of protons ALWAYS equals the number of electrons in a question like this.
This carbon atom is neutral, meaning it's charge is 0. Since neutrons don't have a charge, you're left with protons, which have a positive charge, and electrons which have a negative charge.
In this case, the protons have a charge of +6. But the atom needs to be neutral.
Therefore, you need 6 electrons. -6 and +6 cancel each other out and make the atom have a charge of 0.